The exponential growth in IP traffic and the technical advances in packet technologies have made it possible to support what was once a distinct set of parallel networks (voice, video, wireless), on one integrated data (packet based) network. This has started a move towards a common packet based network with sharing of common network infrastructure to provide services, and interoperability of these services.
The main thrust of technologies in the new packet based network is to carry multiple services of higher value over the existing infrastructure, which in the past would have supported only a single service of lower value. This is particularly true of the ‘last mile’ access infrastructure, where it is highly desirable to not build a separate connection to each customer to enable each new service. Today, the parallel networks tend to merge into a common data based backbone while employing multiple technologies in access (wireline, wireless, cable, satellite). In addition, there is a trend to enable packet based networks with a new set of feature-rich multimedia communication services, such as integrated messaging, multimedia conversations, on-demand multi-point conference, enhanced security & authentication, various classes of media transport services, numerous automations in electronic Internet commerce activities (banking, shopping, customer care, education, etc.).
The current wireless network consists of wireless based access and roaming capabilities that inter-operate with a wireline PSTN backbone infrastructure to provide interoperable PSTN services. As the backbone evolves towards a common packet based core network, the wireless PSTN access infrastructure also evolves to provide wireless PSTN access services while utilizing the new core network. The wireless terminals become IP enabled to allow mobility to the wireline IP based service capabilities (e.g. web browsing, e-mail etc.). In addition, new broadband wireless access emerges to provide a new set of IP enabled services.
A large set of services delivered over a shared broadband network, and in particular across DSL access, have an acceptable fit in terms of performance, availability and security. However, there is another set of services for which today's solutions for broadband delivery may not be acceptable. Examples of such services are fire alarms, burglar alarms, transaction networks (e.g. for debit and credit card transactions), data links to ATMs (Automatic Teller Machines), telemetry information for instrumentation and control system applications, and 1st line telephony.
These services are usually specified as requiring “5 9's”; in other words, availability exceeding 99.999%. Such high availability is especially important where regulatory constraints exist about the reliability with which the respective service may be reached, such as is often the case with critical security or emergency services.
There is currently no known feasible solution for cost effectively enabling such high reliability in non-duplicated wireline access. The existent broadband delivery architectures cannot deliver the specified ‘at least five 9's service availability’ at a competitive cost. Attempting to achieve this level of availability purely on the wireline network would result in duplication of assets and over-engineering of large portions of the access, aggregation and core network, which would then render them too expensive to support the other services which they must carry, such as high speed Internet access.
The current solution to producing high availability networks is not just providing over-capacity (in the sense of higher capacity), but also network duplication. This means that the provider needs to install two of everything (e.g. two wireline access links) and then connect the installed duplicate devices so that any single point of failure does not take out all available capacity. This is expensive; hence a high-availability solution that uses only a single wireline connection is indeed very desirable.
Where duplicate links already exist to a customer to increase availability, these are normally configured to use all the links to the full extent possible. Existing link aggregation solutions such as Ethernet Link Aggregation per IEEE standard 802.3ad or ML PPP (Multi-Link Point to Point Protocol) per IETF RFC1717 and RFC1990 assume that where multiple functional links exist, they will all be used.
The existing standards for ‘link aggregation’ are not concerned with a backup wireless link where the backup is only to be employed as a last resort to maintain connectivity for the set of services mentioned above that require high availability, when the wireline link to a customer becomes unavailable.
There is a need to provide high availability broadband connections for such critical, low volume data services traditionally carried over the PSTN (Public Switched Telephone Network).